Intraoperative neuroelectrophysiological monitoring system

DETAILED DESCRIPTION The neuroelectrophysiological monitoring system of FIG.
1 includes hand operated switches 7, 39, and 24 which respectively: enable "stimulus artifact muting"; enable "electrosurgery muting"; and select between a "fixed recovery period" and a "variable recovery period" in the case that "electrosurgery muting" has been selected.
The system also includes manual adjustments 5, 17 and 35 which respectively: set the muting period when switch 7 has been operated to select "stimulus artifact muting"; set the threshold of the electrosurgery signal that will initiate "electrosurgery muting" when switch 39 has been operated; and set the recovery period when "electrosurgery muting" and "variable recovery period" are selected.
During periods of neuroelectrophysiological monitoring of a surgical patient, stimuli from the electrical stimulation and synchronizing signal source 1 are conducted to selected sites of a surgical patient by the conductors 2.
The resulting electrophysiological response signals are conducted from a patient by the monitoring electrodes 41.
As seen in the figure, there are a plurality of stimulus channels 2 and a corresponding plurality of monitoring channels 41.
The signals from the monitoring electrodes on conductors 41 are processed in the signal conditioning circuitry 42 to provide signals of the appropriate electrical characteristics for the input of the recorder 46.
The signal source 1 provides synchronizing signals to the pulse generating circuit 4 via the conductor 3.
The synchronizing signals are coordinated in time with the stimulus signals.
The pulse generating circuit 4, in response to the synchronizing signals, generates corresponding output signals on conductor 6.
The duration of the output pulses is adjustable from 0.
1 millisecond to 10 milliseconds by means of the pulse width adjustment 5.
When the stimulus muting function has been selected by operation of switch 7, the signals on conductors 6 and 8 will enable the AND gate 9 for a period of time substantially equal to the width of the output pulse of the pulse generator 4